It is well known that warm air forced into a room or derived from radiators tends to rise toward the ceiling of a room while cooler air tends to accumulate near the floor. This produces a temperature gradient that exposes individuals to colder room air during winter months and increases heat loss through ceilings and roofs. A corresponding problem arises during summer months. Individuals may experience a room as being hot because cool air discharged from air conditioning units tends to settle to the floor. Thermostat setting are often changed to obtain more heat or more cool air. In either case, the net result is increased energy consumption and higher cooling and heating costs.
It is also well known that ceiling fans can reduce room temperature gradients and consequently heating costs. The air flows from a ceiling fan tend, however, to spread rapidly, reducing the ability to affect temperature differentials. It is now common practice to use an air flow producer that produces a vertical column of air if significant temperature gradients and attendant heating and air conditioning costs are to be reduced.
A particular producer configuration is used for drop ceilings. Such ceilings have a framework, usually an assembly of T-bars and hangers that suspend the T-bars from a supradjacent ceiling. The framework defines rectangular openings with standard dimensions in which ceiling panels are seated. Building codes often specify that air flow producers used in drop ceilings are not to draw air from the plenum above. In such applications, an air flow producer must both receive and discharge air from below the drop ceiling. Such devices are identified in this specification as “drop ceiling air flow producers” or with comparable terms.
Prior art drop ceiling producers have commonly used a rectangular housing that conforms to dimensions of a seating opening and the rectangular seating structure surrounding the opening. Apart from seating the producer, this arrangement closes the opening against immediate intake of plenum air. Intake and discharge zones are defined in a flow grill overlaying the open bottom of the housing. A fan with a rotary blade assembly is mounted centrally within the housing, and a circular band surrounds the blade assembly to separate intake and discharge air flows. The band forces air flows from the fan through a circular discharge zone centered in the flow grill. Peripheral sections of the grill serve as an intake zone to supply air to the fan. To avoid custom fabrication, the flow producer will usually be manufactured with a standard square housing whose sides conform to standard spacing between drop ceiling rails, usually 24 inches. During installation, the rails of the drop ceiling are adjusted to define a square opening and seating structure that accommodate the square producer.
Such air flow producers have been promoted as being very efficient for production of high-volume, columnar air flows. However, the inventors have discovered that an alternative configuration tends to be more efficient and can be adapted to fit into standard rectangular openings in a drop ceiling framework.